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Biodegradation in water and sediment: simulation tests

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Reference
Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
Data is from computational model developed by USEPA
Qualifier:
according to guideline
Guideline:
other: Modeling database
Principles of method if other than guideline:
Fugacity Model by EPI Suite estimation database
GLP compliance:
not specified
Specific details on test material used for the study:
- Name of test material (IUPAC name): 4-tert-butylcyclohexanol
- Molecular formula : C10H20O
- Molecular weight : 156.267 g/mol
- Smiles notation : C(C1CCC(O)CC1)(C)(C)C
- InChl : 1S/C10H20O/c1-10(2,3)8-4-6-9(11)7-5-8/h8-9,11H,4-7H2,1-3H3
- Substance type: Organic
- Physical state: Solid
Radiolabelling:
not specified
Oxygen conditions:
other: estimation
Inoculum or test system:
not specified
Parameter followed for biodegradation estimation:
test mat. analysis
Details on study design:
Level III Fugacity model
EPI Suite contains a Level III fugacity model. In general, fugacity models predict the partitioning of an organic compound in an evaluative environment. A Level III model assumes steady-state but not equilibrium conditions. The Level III model in EPI Suite predicts partitioning between air, soil, sediment and water using a combination of default parameters and various input parameters that may be user defined or estimated by other programs within EPI Suite.

The model environment consists of 4 main compartments: air, water sediment and soil. There are also sub-compartments such as an aerosol phase, suspended solids, and biota phase, within specific main compartments. A fixed temperature of 25ᵒC is assumed. Mass transport between the compartments via volatilization, diffusion, deposition and runoff are modeled. level III models is a steady state, non-equilibrium model. Steady state conditions mean that the change in concentration of a chemical in each compartment (i) with respect to time eventually approaches zero. The model does not assume that a common equilibrium (fugacity) exists between the phases, so if a chemical is emitted into one compartment it can partition to the other compartments. Loss of chemical occurs through two processes: reaction and advection. Reaction is the biotic or abiotic degradation of the chemical that is calculated using the user specified or model calculated half-lives of the chemical in each of the 4 main compartments. Advection processes are considered for the air, water and sediment compartments. Advection is the removal of chemical from a compartment through losses other than degradation (reaction). The rate of advection in a given compartment is determined by a flow rate (m3/hour), calculated by dividing the volume of the compartment by an advection time.
Compartment:
water
% Recovery:
28.4
Remarks on result:
other: Other details not known
Compartment:
sediment
% Recovery:
0.141
Remarks on result:
other: Other details not known
Key result
% Degr.:
50
Parameter:
other: Half-life in water
Sampling time:
15 d
Remarks on result:
other: Other details not known
Key result
% Degr.:
50
Parameter:
other: Half-life in sediment
Sampling time:
135 d
Remarks on result:
other: Other details not known
Key result
Compartment:
water
DT50:
15 d
Type:
other: estimated data
Temp.:
25 °C
Remarks on result:
other: Other details not known
Key result
Compartment:
sediment
DT50:
135 d
Type:
other: estimated data
Temp.:
25 °C
Remarks on result:
other: Other details not known
Transformation products:
not specified
Evaporation of parent compound:
not specified
Volatile metabolites:
not specified
Residues:
not specified

Mass Amount

(percent)

Half-Life (hr)

Emissions (kg/hr)

Water

28.4

360

1000

Sediment

0.141

3.24e+003

0

 

Fugacity (atm)

Reaction (kg/hr)

Advection (kg/hr)

Reaction (percent)

Advection (percent)

Water

2.42e-010

683

355

22.8

11.8

Sediment

2.11e-010

0.377

0.0353

0.0126

0.00118

Validity criteria fulfilled:
not specified
Conclusions:
Estimated half life of test chemical 4-tert-butylcyclohexanol in water was 15 days (360 h) and in sediment estimated to be135 days (3240 h).
Executive summary:

Estimation Programs Interface (EPI Suite, 2018) prediction model was run to predict the half-life in water and sediment for the test compound 4-tert-butylcyclohexanol (CAS No. 98 -52 -2). If released in to the environment, 28.4% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 4-tert-butylcyclohexanol in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 4-tert-butylcyclohexanol in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.141%), indicates that 4-tert-butylcyclohexanol is not persistent in sediment.

 

Description of key information

Estimation Programs Interface (EPI Suite, 2018) prediction model was run to predict the half-life in water and sediment for the test compound 4-tert-butylcyclohexanol (CAS No. 98 -52 -2). If released in to the environment, 28.4% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 4-tert-butylcyclohexanol in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 4-tert-butylcyclohexanol in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.141%), indicates that 4-tert-butylcyclohexanol is not persistent in sediment.

 

Key value for chemical safety assessment

Half-life in freshwater:
15 d
at the temperature of:
25 °C
Half-life in freshwater sediment:
135 d
at the temperature of:
25 °C

Additional information

Various predicted data for the target compound 4-tert-Butylcyclohexanol (CAS No. 98-52-2) were reviewed for the biodegradation in water and sediment end point which are summarized as below:

 

In aprediction done using the Mackay fugacity model level III of Estimation Programs Interface (EPI Suite, 2018) was run to predict the half-life in water and sediment for the test compound 4-tert-Butylcyclohexanol (CAS No. 98-52-2).If released in to the environment, 28.4% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 4-tert-butylcyclohexanol in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 4-tert-butylcyclohexanol in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.141%), indicates that 4-tert-butylcyclohexanol is not persistent in sediment.

 

In a supporting study from secondary source (Robust Summaries & Test Plans: Cyclohexy Derivatives Category: Revised Summaries, 2006) and HPVIS, 2017, half-life of the chemical 4 -tert-Butylcyclohexanol (CAS No: 98-52-2) in water and sediment by using Mackay EQC Fugacity Level III. The following values has been used in the Mackay EQC Fugacity Level III for the estimating the half-life value. They are water solubility: 100 mg/l, vapour pressure: 0.0075 mm Hg, log Kow: 3.23 and melting point: 55-70°C, respectively. If released into the environment, 38.1% of the chemical will partition into water according to the Mackay EQC Fugacity Level III and the half-life period of 4 -tert-Butylcyclohexanol in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by Mackay EQC Fugacity Level III) indicates that the chemical 4-tert-Butylcyclohexanol is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 4-tert-Butylcyclohexanol in sediment is estimated to be 60 days (1440 hrs). Based on this half-life value of test chemical 4-tert-Butylcyclohexanol, it is concluded that the chemical 4-tert-Butylcyclohexanol is not persistent in the sediment environment and the exposure risk to soil dwelling animals is moderate to low.

 

On the basis of above results for target chemical 4-tert-Butylcyclohexanol (from EPI suite, 2018 and secondary source), it can be concluded that the test substance 4-tert-Butylcyclohexanol is not persistent in the water and sediment environment and therefore the exposure risk to aquatic and soil dwelling animals is moderate to low.